You've got this

Also, You got this.
Encouragement when a person really doubts that they can do something. The speaker thinks the person can do it successfully. The speaker may or may not actually know.

The speaker may use it as a way to end a conversation, or to encourage the person to shut up about it, already.

Synonym: Just do it.
May or may not actually encourage or help the person who doubts their ability.

Doubtful person: I haven't been able to get myself to stop eating too much junk food.
Deluded person: You can stop. You've got this.